A22: Storage
classes define the scope, lifetime, and visibility of variables within a
program. Each variable in C has a storage class, which determines how the
variable is stored in memory and how it can be accessed.
There
are four storage classes in C:
1. Automatic
Storage Class (auto):
Memory allocated and deallocated
automatically to the variable.
They are used for local variables.
Variable contains garbage value unless
initialized.
2. Register
Storage Class (register):
It is same as auto but variable stored in CPU
registers.
‘register’ keyword is a hint to compiler to
optimize access.
The variable does not have any memory
location.
3. Static
Storage Class (static):
Variable has fixed memory location throughout
the program.
They are initialized only once, and their
values persist.
They are accessible within the entire source
file.
They are initialized to zero by default.
4. External
Storage Class (extern):
The variables which are declared outside all
function are known as external variables.
They can be used by all the function.
The ‘extern’ keyword is used to declare
variable.
